This invention relates generally to circuit breakers and more specifically relates to a pinless conducting joint and variable pivot point in a movable contact arm assembly which permits the contact arm to have a greater degree of freedom in response to high current events.
Electrical distribution devices are well known in the art. A conventional circuit breaker includes a pair of contacts which allows circuit current to pass from one contact member to the other contact member. A typical circuit breaker uses a movable contact structure in which one contact is disposed at a stationary location, such as a stationary contact arm, while the other contact is disposed on a movable contact arm. The movable contact arm generally comprises a pivoted contact arm for making and breaking the circuit at a single location. The movable contact arm is usually connected to a conducting support at one end of the contact arm, wherein the opposite end includes the contact. The connection between the contact arm and the conducting support is made by using a contact arm pivot pin in which the contact arm pivot pin extends through an aperture in the contact arm and in the conducting support.
The use of the pivot pin permits rotation of the contact arm about the pivot pin so that the contact arm rotates about the pivot pin to separate the contacts. One limitation of using a pivot pin for a conducting joint formed by the connection between the conducting support and the contact arm is that the contact arm can only rotate in an opening direction. In response to magnetic forces of high current, non-trip condition, the contact of the breaker will rotate a small angle in the open direction, failing to maintain contact.
Typically, the circuit breaker and more specifically, the contact arm assembly thereof, includes a second pin or moving stop which interacts with the movable contact arm assembly to insure that all of the movable contact arms operate in unison when the operating mechanism is articulated. Thus, when the second pin or moving stop is moved in response to the actuation of the operating mechanism, current is prevented from flowing through each of the contact arm assemblies and the load is protected.